During the combustion process in an IC engine (e.g., a diesel IC engine), sulfur may be concurrently formed with carbon monoxide (CO) and hydrocarbons (HC) as various sulfur oxides (SOx). Typically, 97-99% of the total amount of SOx present in exhaust gas comprises sulfur dioxide (SO2), and 1-3% comprises sulfur trioxide (SO3). Thus, fuel with higher sulfur content tends to produce higher amounts of SO3. For example, fuel with sulfur content of 1,000 ppm may form approximately 1-3 ppm SO3.
Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by IC engines. Conventional exhaust gas aftertreatment systems include any of several different components to reduce the levels of harmful exhaust emissions present in exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a selective catalytic reduction (SCR) catalyst to convert NOx (NO and NO2 in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3).
Oxidation of SO2 present in the exhaust gas can lead to an increase in SO3 content of the exhaust gas, e.g. due to oxidation of SO2 to SO3. The SO3 can react with ammonia provided by the reductant to produce ammonium sulfate ((NH4)2SO4) and ammonium bisulfate (NH4HSO4), which can reduce the amount of ammonia available for facilitating decomposition of NOx gases within the SCR system. Furthermore, the higher SO3 content can also reduce a filtering efficiency of one or more particulate sensors included in the aftertreatment system and/or poison one or more oxidation catalysts included in the aftertreatment system.